Seasonal Dynamics and Damages of Mononychellus tanajoa Bondar (Acari: Tetranychidae) on Commercial Cassava Varieties in Mwanza Region, Lake Zone,Tanzania

Abstract

Two-year studies were conducted to determine the responses of 9 commercial and local cassava varieties to M. tanajoa and the environment during the 2014/2015 and 2015/2016 wet and dry seasons at Ukiriguru in Mwanza region of the Lake Zone, Tanzania. The experiments were conducted at Lake Zone Agricultural Research and Development Institute, Ukiriguru. These were laid out in a Randomized Complete Block Design (RCBD) with three replications, making a total of twenty-seven plots allocated to a plot size of 36m2with a 1m path between plots and 2m between blocks. One stem cutting (30cm long) was planted at a spacing of 1x1m within and between rows giving a total of 10,000 plant population ha-1. This was allowed under natural infestation by the mites. Results revealed that the population and damage were higher in 2016 while leaf malformation and mites incidence were statistically greater in 2015. Cassava varieties were heavily infested and damaged at lower age range (3 and 6 months) within and between the two seasons. Among the crop varieties, Liongo Kwimba recorded higher infestation and suffered most in leaf damage and malformation. Kyaka cassava variety was found to performed better in yield despite the attack by the mites while Liongo Kwimba recorded the lowest yield. The regression analysis predicted mostly negative relationships among the weather variables and the population, damage and incidence of M. tanajoa. Therefore, farmers at Ukiriguru could be encouraged to plant Kyaka variety for increased yield while Liongo Kwimba should be improved especially by breeding and molecular researches. More so, there is need to manipulate planting season by early planting before the favourable period of growth and perpetuation of M. tanajoa.